1. Field of the Invention
The present invention relates to a fabrication method of a light emitting diode package, more particularly, which can achieve excellent heat radiation as well as facilitate mass production.
2. Description of the Related Art
Recent development of Light Emitting Diode (LED) devices made of compound semiconductor material such as GaAs, GaN and AlGaInP has enabled lighting sources of various colors. Decisive factors of LED properties may include color, brightness and optical conversion efficiency. While such LED properties are primarily determined by compound semiconductor material and its internal structure used for an LED device, a package structure for housing the LED device acts as a secondary factor, giving great influence on the LED properties. In order to realize light emitting efficiency to such a degree that can satisfy user demand, it is necessary to improve not only first factors such as the material and structure of an LED device but also secondary factors such as an LED package structure and its material.
In particular, as LED application is spreading to various fields such as interior and outdoor illumination, automobile headlight, backlight unit of a display system, high efficiency and high heat radiation have become necessary. If heat is not efficiently radiated from an LED device, it raises the temperature of the LED device, thereby deteriorating LED device properties while shortening its lifetime. Accordingly, various endeavors have been made to effectively radiate heat out of the LED device. As an approach for improving heat radiation characteristics of an LED package, Japanese Laid-Open Patent Application No. 2003-218398 proposes to use a metal substrate divided by a narrow slot as an LED package substrate. Besides, Japanese Laid-Open Patent Application 2003-163378 discloses an approach for fabricating a package substrate which is divided by a narrow slot and made integrally with a reflector.
FIG. 1 is a cross-sectional view schematically illustrating the structure of a conventional LED package 10. Referring to FIG. 1, the LED package 10 includes a package substrate 1 made of metal. The package substrate 1 is divided into two package electrodes 1a and 1b by a slot 6 where insulator 2 of for example epoxy resin and so on is filled. The package substrate 1 has a recess 3, such that an LED device 7 is flip-chip bonded onto the package electrodes 1a and 1b at the bottom of the recess 3. Underfill resin 4 is filled between the LED device 7 and the bottom of the recess 3. A cover panel 9 made of glass is bonded onto the top of the package substrate 1. Sidewall of the recess 3 forms a reflector surface 1c, which reflects light propagating in lateral direction to redirect it in upward direction.
FIGS. 2a to 2d are cross-sectional views illustrating a fabrication process of an LED package as shown in FIG. 1. Referring to FIG. 2a first, a package substrate 1 having a reflector surface 1c in a recess 3 is formed by molding or press molding of metal. Then, as shown in FIG. 2b, a slot 6 is formed in the package substrate 1, dividing it into two package electrodes 1a and 1b. The slot 6 is formed by machining such as press trimming or laser processing. Insulator 2 of for example epoxy resin is filled into the slot 6, and through flip-chip bonding, an LED device 7 is mounted on the package electrodes 1a and 1b at the bottom of the recess 3 as shown in FIG. 2c. Underfill resin is also filled between the LED device 7 and the bottom of the recess 3. Then, as shown in FIG. 2d, a cover panel 9 made of glass is bonded onto the top of the package substrate 1, thereby producing an LED package as shown in FIG. 2d. 
Since the package substrate 1 is made of metal, it can effectively radiate heat from the LED device 7. However, in order to fabricate the LED package 10, a metal substrate (i.e., package substrate) has to be machined precisely so that the package substrate 1 is divided by the narrow slot 6, and insulator 2 has to be filled into the narrow slot 6. However, there is no easy way to from the narrow slot 6 in the metal substrate by machining or laser processing. This as a result causes high defective proportion as well as poor yield.